Portable speaker assembly for large areas



Sept. 1, 1970 D. L. BEATTY 3,526,718

PORTABLE SPEAKER ASSEMBLY FOR LARGE AREAS Filed April 17, 19,67 2Sheets-Sheet 1 f f 1 M I g y 1 5P6 X t I i l l l l J4 I Jl 4 If 2INVENTOR. David 1. fleafly BY I E A ffor'ney.

Sept. 1, 1970 D. BEATTY PORTABLE SPEAKER ASSEMBLY FOR LARGE AREAS 2Sheets-Sheet 2 Filed April 17, 1967 a F i l} INVENTOR. Dar/a L fieaflyUnited States Patent 3,526,718 PORTABLE SPEAKER ASSEMBLY FOR LARGE AREASDavid L. Beatty, 10712 E. 84th Terrace, Raytown, Mo. 64138 Filed Apr.17, 1967, Ser. No. 631,346 Int. Cl. H04r 1/02, 27/00 US. Cl. 1791 1Claim ABSTRACT OF THE DISCLOSURE This invention relates to new anduseful improvements in speaker assemblies for public address systems andthe like, and has particular reference to speaker systems especiallyadapted for use in servicing large areas such as auditoriums, fieldhouses, concert halls and similar buildings, as well as outdoor areassuch as parking lots, Where public gatherings are often held.

Modern requirements for high-fidelity sound reproduction in systems ofthis type require the use of separate speakers for high and low soundfrequencies, in order that faithfully accurate sounds may be providedthroughout the entire sound spectrum. However, the high-intensity soundlevels required from the speaker system in order to blanket large areasas described with sounds at an acceptable level create certain problemsin that the sound level is often oppressively intense, and even painful,for persons who must be close to the speakers. This undesirableoccurrence is particularly noticeable in connection with soundsemanating from the high-frequency speakers, or tweeters, since while thelow-frequency sounds tend to be rather non-directional or pervasive, sothat to the listener they seem to come from no accurately detectablesource but to come from all directions, and further are not particularlyoppressive to the ear even when of very high intensities, high-frequencysound has very different characteristics. The sound Waves emanating fromhighfrequency tweeters or horns tends to be rather highly directional,proceeding from the speaker in a rather tightly restricted conical zone.The sound can be somewhat diffused, and the angle of the conical zonesomewhat enlarged, but the speaker must still be aimed or directed muchmore accurately toward the listeners than is the case with thelow-frequency speaker. Moreover, the high-frequency sound at highintensities is much more oppressive to the ear of the listener thanlow-frequency sound, having a greater apparent loudness, and thuscreates discomfort and poor listening for those who must becomparatively close to the speakers. At the same time, the highintensity is necessary if the high-frequency sounds are to carry to thefar reaches of large areas. Another comparative characteristic of highand low frequency sounds is that obstructions in the path ofhigh-frequency sounds produce a pronounced shadow effect, tending tocreate a zone therebehind in which the sound cannot be heard, or can beheard only faintly. This shadow effect, being an inverse function of thewave length of the sound, is much less with low-frequency sound, saidlow-frequency sound apparently flowing around obstructions, andrequiring a much larger obstruction to produce a shadow. While all ofthe above considerations can of course be 3,526,718 Patented Sept. 1,1970 taken into account in a carefully designed permanent installation,they heretofore have presented a problem not solved in connection Withportable equipment adapted to be transported easily from place to placewith a minimum requirement of assembly and disassembly, installation orset-up time, and the like.

Accordingly, the principal object of the present invention is theprovision of a portable speaker assembly for large areas which largelyovercomes all of the above objectionable features of existing systems,in that it provides adequate coverage of large areas with sound at anacceptable level, without at the same time blasting the ears oflisteners who must be relatively close to the speakers. Generally, thisobject is accomplished by the provision of an assembly including afloor-engaging base cabinet in which the low-frequency speakers aremounted, and a high-frequency speaker mounted in spaced relation abovesaid base cabinet and so directed or aimed that its sound axis isdisposed well above the heads of nearby listeners. The base cabinetprovides the mass and resonance chamber required for best performance oflow-frequency speakers, as well as serving as a supporting base for thehighfrequency speaker, and the low elevation of these speakers isacceptable since the low-frequency sound will not be oppressive tonearby listeners, or shadowed by said nearby listeners or otherobstructions. Since the high-frequency speaker is directed over theheads of nearby listeners, they hear the high-frequency sound asspillage or diffusion from the main sound cone of the speaker, and thusare not subjected to its full direct force, so that the high-frequencysounds are not oppressive. At greater distances from the speaker, thelisteners will be angularly closer to the extended axis of the speaker,so that the high-frequency sound level will tend to be equalized at alldistances within range. Both the elevation and vertical angle ofinclination of the high-frequency speaker may be adjusted to the sizeand contour of the area being served, as will be described.

Another object is the provision of a speaker assembly of the characterdescribed having structural features contributing substantially to theease of transportation, handling and use thereof.

With these objects in view, as well as other objects which -will appearin the course of the specification, reference will be had to theaccompanying drawing, wherein:

FIG. 1 is a front elevational view of a speaker assembly embodying thepresent invention, with the cabinet doors closed,

FIG. 2 is a side elevational view of the assembly as shown in FIG. 1,with parts broken away,

FIG. 3 is a fragmentary rear elevational view of the assembly,

FIG. 4 is an enlarged fragmentary sectional view taken on line IVIV ofFIG. 3,

FIG. 5 is an enlarged fragmentary sectional view taken on line V-V ofFIG. 3,

FIG. 6 is an enlarged fragmentary sectional view taken on line VIVI ofFIG. 1,

FIG. 7 is an enlarged fragmentary sectional view taken on line VII-VIIof FIG. 1, and

FIG. 8 is a sectional view taken on line VIIIVIII of FIG. 1, with thecabinet doors open.

Like reference numerals apply to similar parts throughout the severalviews, and the numeral 2 applies generally to a base cabinet normallyresting on the floor or ground 4 as shown in FIGS. 1 and 2. Said cabinetis generally rectilinear in form, having side walls 6, top wall 8,bottom wall 10, and back wall 12. The front of said cabinet comprises aspeaker face 14 of grill cloth or the like (see FIGS. 6 and 7) behindwhich, within the cabinet, are mounted one or more low-frequencyspeakers, or woofers, these speakers being indicated at 16 in FIG. 1.The

speaker face may be covered and protected by a pair of rigid doors 18,each door being secured at its outer vertical edge to the forward edgeof the corresponding side wall 6 by means of a piano-type hinge 20. Eachdoor covers half of the cabinet front, said doors being shown closed inFIG. 1 and open in FIG. 8. It will be noted that said doors extenddownwardly to floor level, and that each door is provided along itsbottom edge with an enlarged foot 22. Thus when the doors are open asshown in FIG. 8, their engagement with the floor causes them to act asstabilizers for steadying the cabinet against vibration or rocking, andto prevent accidental overturning thereof by wind or the jostling ofpersons thereagainst.

A recess 24 is formed in the cabinet opening outwardly through the upperportion of back wall 12. Mounted in said recess, respectively adjacentopposite sides of the cabinet, are a pair of castered wheels 26, saidwheels projecting outwardly from said back wall as best shown in FIG. 4.Back wall 12 overhangs at least the upper edge portion of recess 24,intermediate said wheels, to form a hand hold 28, for a purpose to bedescribed. Terminal posts 30, for making electrical connections to thespeakers within the cabinets, may also be positioned in recess 24, forprotection thereof against damage from bumping. A pair of recesses 32are formed in the cabinet at the lower rear portion thereof, saidrecesses opening through back wall 12 and bottom wall of the cabinet,respectively adjacent opposite sides thereof. Mounted rotatably in eachof recesses 32 is a ground-engaging wheel 34, said wheels being coaxialon a horizontal transverse axis. As best shown in FIG. 5, wheels 34project outwardly from back wall 12, but are spaced slightly above thebottom of the cabinet when said cabinet is upright. When the cabinet istilted rearwardly, using hand hold 28 as a grip, wheels 34 engage theground, and the cabinet may be moved or transported in the manner of awheelbarrow. The juncture between back wall 12 and bottom wall 10 may berounded as indicated at 36 to facilitate this action. Also, the cabinetmay be tilted to lie on its back, all of wheels 26 and 34, then engagingthe ground, and the cabinet may then be moved about or transported inthe manner of a fourwheeled cart, the castering of wheels 26 permittingsteering thereof. In this case, the closed doors 18 serve as a platformfor carrying the high-frequency speaker (to be described below) or othersupplies.

Extending upwardly from top wall 8 is a standard 38 consisting of aheavy rod or pipe. The lower portion of said standard is carried forlongitudinal sliding movement in a tubular guide 40 extending verticallythrough cabinet 2, centrally thereof, and rigidly mounted therein. Thisguide will not ordinarily interfere with the placement of bass speakers16 in the cabinet, since the speakers are mounted in the forward portionthereof, the excess cabinet space providing the resonance chamberrequired for best performance of said speakers. The cabinet may also beprovided with tube vents, not shown, to still further improve the soundquality of the speakers. Standard 38 is vertically adjustable in guide40, being secured at the desired extension by means of a collar 42 fixedthereon by set screw 44 and resting by gravity on top cabinet wall 8.

A sleeve 46 is mounted slidably on standard 38 adjacent the upper endthereof, and adjustably fixed thereon by set screw 48. Fixed to saidsleeve, as by bolts 50, is a horizontally extending arm 52. To the outerend of said horizontal arm an upwardly arm 54 is attached, by means ofhinge 56, the axis of said hinge being transverse to standard 38 andoffset transversely therefrom. A high-frequency speaker, or tweeter," 58is attached fixedly to arm 54 as by bolts 60. Usually said speaker ismore or less horn-shaped, often being called a horn, and is ordinarilydirected or aimed to project sound more or less horizontally. Said hornprojects over the upper end of standard 38, which projects above sleeve46, and rests on said standard by gravity. It will thus be seen that thevertical angle of inclination of the horn can be adjusted by looseningset screw 48 and sliding sleeve 46 up or down on the standard. Aspreviously noted, the sound from such a speaker is highly directional,tending to be confined to a conical zone concentric with the speakeraxis. This can be partially corrected, and the sound cone flattened tocover a larger horizontal area, by means of a sound lens 62 comprising,as shown, a series of specially configurated parallel plates attached tothe forward end of the horn. This lens, however, forms no essential partof the present invention, and the construction and operation thereof isnot detailed herein.

In operation, it will be seen that the structure shown takes advantageof the natural characteristics of the high and low frequency sounds andthe requirements for effective distribution thereof. The low-frequencyor bass speakers 16 require a massive enclosure and a voluminousresonance chamber for best performance, and cabinet 2 provides this massand volume. Its considerable mass also provides good support andfoundation for the high-frequency speaker 58. Moreover, it is quitesatisfactory that the bass speakers be disposed substantially atear-level of the listeners, even if the low-frequency sound intensitymust be at a high level to blanket a large listening area, and even ifsome listeners must be relatively close to the speakers, since aspreviously discussed, low-frequency, high-intensity sounds are notoffensive to the ear. Furthermore, the nearby listeners themselves, orother obstructions, will not prevent the low-frequency sounds fromreaching distant listeners, since obstructions have very little shadoweifect on sounds of long wave length.

On the other hand, the high-frequency sounds emanating from speaker 58are directed outwardly over the heads of the listeners, as previouslydescribed, in a rather highly directional conical zone, or a zone offlattened conical form, concentric with the axis of the speaker. Thus,nearby listeners will be disposed in the lower peripheral portion of thesound cone, or entirely below said sound cone, in which latter case theyhear the high-frequency sound as diffusion or spillage from the soundcone. In other words, their angular displacement from the speaker axisis relatively great, and due to the directional nature of this sound,they are subjected only to a fraction of the sound intensity which theywould receive if they were positioned directly in the speaker axis.Thus, even nearby listeners are not subjected to the oppressive or evenpainful effects of high-intensity, high-frequency sound. More distantlisteners, however, by virtue of the distance, will be positioned atless angular displacement from the speaker axis, and are hence subjectedto a progressively greater proportion of the full sound intensity atthat distance. If speaker 58 is properly positioned and directed, theapparent or effective loudness of the high frequency sound will tend tobe equalized at all distances from the speaker within the design rangeof said speaker.

With regard to proper placement of speaker 58, its elevation from basecabinet is a function of the distance to the furthest portion of thelistening area, greater required distances requiring speaker 58 to beelevated progressively higher to avoid oppressive loudness to nearbylisteners. This elevation can of course be adjusted by loosening setscrew 44 and sliding standard 38 up or down in guide 40. If stillgreater elevations are desired, standard 48 could be formed of multipletelescoped sections, within the scope of the invention. With regard tothe angle of inclination of speaker 58, it-has been found in mostinstances that the speaker axis should be aimed at the ear level of themost distant listeners, and the sound intensity set to deliver sound atan acceptable intensity at that distance to listeners directly in linewith the extended axis of the speaker. This may require the speaker tobe directed slightly downwardly if the listening area is horizontal orupwardly in varying degrees if the listening area slopes upwardly awayfrom the speakers, as in an amphitheater. The angle of inclination ofspeaker 58 can of course be adjused in the present structure byloosening set screw 48 and sliding sleeve 46 up or down on the standard.

While I have shown and described a specific embodiment of my invention,it will be readily apparent that many minor changes of structure andoperation could be made without departing from the spirit of theinvention as defined by the scope of the appended claim.

What I claim as new and desire to protect by Letters Patent is:

1. A portable speaker assembly for large areas comprising:

(a) a floor-supported base enclosure comprising a cabinet having avertical tubular guide mounted therein.

(b) a low-frequency speaker mounted in said base enclosure,

(c) a standard mounted in said base enclosure and projecting upwardlytherefrom, said standard being vertically slidable in said tubularguide,

((1) a high-frequency speaker mounted at the upper end of said standardand operable to project sound, which is principally confined to alimited zone coaxial with the extended axis of said speaker,

(e) means for adjusting the degree of vertical projection of saidstandard above said base enclosure comprising a collar slidably mountedon said standard and resting on the top of said cabinet, and meansreleasably fixing said collar on said standard, and

(f) means for adjusting the angle of vertical inclination of saidhigh-frequency speaker comprising a sleeve mounted slidably on saidstandard in spaced relation below the upper end thereof, meansreleasably fixing said sleeve on said standard, a first arm fixed tosaid sleeve and projecting horizontally there- UNITED STATES PATENTS1,782,660 11/1930 Meyer 179-148 X 2,143,175 1/1939 Waite. 2,203,715 6/1940 Benecke. 2,288,822 7/1942 McCarron 179l48 3,165,587 1/1965Alderson. 3,183,305 5/1965 Jespersen. 3,308,237 3/1967 Novak.

OTHER REFERENCES Column Loudspeaker Systems; Augspurger, George L.,

Electronics World, June 1963, pp. 25-26.

KATHLEEN H. CLAFFY, Primary Examiner C. W. JIRAUCH, Assistant ExaminerUS' Cl. X.R.

